Justice Antonin Scalia's unexpected death in February and the Senate's refusal to confirm a successor has left the Supreme Court in a bind on several closely divided cases.

Even as some justices have said the short-handed court will continue to get its work done, Justice Ruth Bader Ginsburg has noted, "Eight is not a good number."

The court's 4-4 tie Thursday in a case about President Barack Obama's plan to help millions of immigrants living in the U.S. illegally was the latest illustration of what Ginsburg meant. The justices were unable to resolve a case without Scalia's vote and unwilling to keep the case on hold for an indefinite period because they don't know when a ninth justice will join them.

The high court has been operating with eight justices instead of its full complement of nine since Scalia died. Obama has nominated Judge Merrick Garland to take Scalia's place, but Senate Republicans have refused to hold a hearing or a vote.

Garland wouldn't have been available to take part in this term's cases even if the Senate had acted quickly on his nomination. But the other justices might have ordered new arguments in some cases in which they split 4 to 4 if they knew Garland would be on the bench by the time the next term begins in October.